Drive device, electronic watch, and control method of drive device

ABSTRACT

A drive device includes a first hand, a second hand, and a control unit that controls a movement operation of the second hand. The control unit starts movement of the second hand in a period after start of movement of the first hand before stop of the movement of the first hand. The control unit controls the movement operation of the second hand according to a decrease in a movement speed of the first hand.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2015-179218, filed on Sep. 11,2015, and the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

The disclosure relates to a drive device for moving hands by steppingmotors, an electronic watch having the drive device, and a controlmethod of the drive device.

For example, in an analog electronic watch disclosed inJP-A-2005-147727, a plurality of stepping motors drives hands such as anhour hand, a minute hand, and a second hand, respectively, whereby timeis displayed. This hand movement is performed by applying drive pulsevoltages to the stepping motors, thereby rotating the rotors of thestepping motors, and transmitting the torque of each rotor to acorresponding hand at a predetermined gear ratio by gear trainmechanisms which are arrangements of gears, thereby rotating the hands.

In the analog electronic watch, for example, during correction oncurrent time or switching of display modes or operation states accordingto or a user's operation on a stem or the like, the output frequenciesof the drive pulse voltages for the stepping motors are controlled,whereby the hands are fast-forwarded.

In the technology disclosed in JP-A-2005-147727, when the plurality ofstepping motors is controlled, after a previous control motor stops, theoperation of the next control motor is controlled.

In the technology of Japanese Patent Application Laid-Open No.2005-147727, the degree of freedom of control on hand movement starttimings and hand movement speeds is low, and it is difficult to expresshand movement more smoothly and more dynamically.

SUMMARY OF THE INVENTION

An object of the disclosure is to provide an electronic watch having ahigh degree of freedom of hand movement and having improvedexpressiveness.

A drive device of the present invention comprises:

a first hand;

a second hand; and

a control unit that controls a movement operation of the second hand,

wherein the control unit starts movement of the second hand in a periodafter start of movement of the first hand before stop of the movement ofthe first hand, and

the control unit controls the movement operation of the second handaccording to a decrease in a movement speed of the first hand.

A control method of a drive device having a plurality of motors and amotor control processing unit configured to control the motors,according to the present invention comprising:

performing control, by the motor control processing unit, such that thedriving speed of one motor of the plurality of motors decreases;

after decreasing the driving speed, performing control, by the motorcontrol processing unit, such that driving of the other motor of theplurality of motors starts, by the motor control processing unit; and

after the start control, controlling a drive signal for the motor tostart to be driven, by the motor control processing unit, such that thedrive signal for the motor to start to be driven is at high level when adrive signal for the motor whose driving speed decreases is at lowlevel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the configuration of a drivedevice for an electronic watch of an embodiment.

FIG. 2A is a view illustrating motor driving timings of an electronicwatch of the related art.

FIG. 2B is a view illustrating motor driving timings of the electronicwatch of the embodiment.

FIG. 2C is a view illustrating other motor driving timings of theelectronic watch of the embodiment.

FIG. 3 is a view illustrating an overview of the specifications ofmotors of the embodiment.

FIG. 4 is a view illustrating a motor control flow of the embodiment.

FIG. 5 is a view illustrating the dial of another electronic watch ofthe embodiment.

FIG. 6 is a block diagram illustrating the configuration of a drivedevice of the electronic watch of FIG. 5.

FIG. 7 is a timing chart for explaining a reset operation of a stopwatchfunction.

FIG. 8 is a view illustrating operation conditions of motors during thereset operation.

FIG. 9 is a view illustrating the flow of control on the motors duringthe reset operation.

FIG. 10 is a timing chart for explaining operations of a flybackfunction of a stopwatch.

FIG. 11 is a view illustrating the control flow of the flyback functionof the stopwatch.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present invention will be described indetail with reference to the accompanying drawings.

FIG. 1 is a block diagram illustrating the configuration of a drivedevice 101 for a wristwatch type electronic watch according to theembodiment. Although the present embodiment will be described withreference to wristwatch type electronic watches, it is not limitedthereto.

The drive device 101 of an electronic watch 100 of the embodimentincludes a disk hand 10 which constitutes a calendar mechanism or thelike of the watch, and other hands, that is, an hour hand 13, asecond/minute interlocking hand 16, and a function hand 19, which rotatein steps of a predetermined angle on a dial. The disk hand 10 is driventhrough a gear train mechanism 11 by a dual-core motor 12. The hour hand13 is driven through a gear train mechanism 14 by a first single-coremotor 15. The second/minute interlocking hand 16 is driven through agear train mechanism 17 by a second single-core motor 18. The functionhand 19 is driven through a gear train mechanism 20 by a thirdsingle-core motor 21.

The dual-core motor 12, the first single-core motor 15, the secondsingle-core motor 18, and the third single-core motor 21 (which willalso be referred to collectively as motors) are stepping motors. A drivecircuit 22 separately applies drive pulses to the motors, therebyrotating the motors. At this time, voltage can be applied to thedual-core motor 12 at a pulse frequency of 192 pps (Pulse Per Second)which is the maximum frequency, whereby it is possible to fast-forwardthe disk hand 10. Also, voltage can be applied to each of the firstsingle-core motor 15, the second single-core motor 18, and the thirdsingle-core motor 21 at a pulse frequency of 64 pps which is the maximumfrequency, whereby it is possible to separately fast-forward the hourhand 13, the second/minute interlocking hand 16, and the function hand19.

The drive circuit 22 is controlled by a micro computer 23, and iscomposed of an H bridge circuit using metal-oxide-semiconductorfield-effect transistors (MOS-FETs). In the above described way, themotors are rotated in a normal direction or a reverse direction.

The micro computer 23 includes a central processing unit (CPU) forperforming arithmetic processing, and retains programs which the microcomputer uses to configure a motor control processing unit 230 a whichis composed of a drive motor selecting unit 2301, a drive pulsegenerating unit 2302, and a parallel-driving determining unit 2303.Specifically, according to the operation mode, the drive motor selectingunit 2301 selects motors corresponding to hands to be moved. As will bedescribed in detail, on the basis of the drive frequencies of the motorsselected by the drive motor selecting unit 2301, the parallel-drivingdetermining unit 2303 determines whether it is possible to drive theplurality of motors in parallel, and if parallel driving is possible,the parallel-driving determining unit 2303 instructs the drive pulsegenerating unit 2302 to generate drive pulses. For each of the motors,the drive pulse generating unit 2302 generates pulse voltage to beapplied to the corresponding motor, for a predetermined time.

As described above, the micro computer 23 functions as a control unitfor controlling movement of the hands.

An oscillator 25 is a crystal oscillator for obtaining a referenceperiod of clocking and a periodic signal which is a reference of theoperation clock of the micro computer 23. The oscillator 25 is driven byan oscillation circuit 231 included in the micro computer 23, and thefrequency of the oscillator is appropriately divided by a frequencydivider circuit 232, and a clocking circuit 233 clocks seconds, minutes,hours, and date.

An operation unit 24 is an operation unit such as a stem or a pushbutton, and is connected to the frequency divider circuit 232 of themicro computer 23, and transmits operation information to the microcomputer 23.

A power source unit 26 supplies electric power to the micro computer 23and the motors such as the dual-core motor 12 and the like. The powersource unit 26 is configured, for example, by combining a secondarybattery and a solar panel.

Now, motor drive control during hand fast-forwarding of the electronicwatch 100 of the present embodiment will be described.

FIG. 2A is a view illustrating motor driving timings of an electronicwatch according to the related art. FIG. 2A shows the outlines of thewaveforms of voltages which are applied to the dual-core motor 12, thefirst single-core motor 15, the second single-core motor 18, and thethird single-core motor 21 shown in FIG. 1. In FIG. 2A, the transversedirection represents elapse of time. In the motor drive control of therelated art, for example, after the dual-core motor 12 stops, a drivepulse is applied to the first single-core motor 15, thereby starting todrive the first single-core motor. In other words, after a specificmotor stops, driving of another motor starts. Therefore, it takes longto move the hands, and expressiveness of movement of the hands is poor.

For this reason, in the electronic watch 100 of the present embodiment,the hands are fast-forwarded at motor driving timings shown in FIG. 2B.

FIG. 2B shows the outlines of the waveforms of voltages which areapplied to the dual-core motor 12, the first single-core motor 15, thesecond single-core motor 18, and the third single-core motor 21 shown inFIG. 1. In FIG. 2B, the transverse direction represents elapse of time.

According to the motor driving timings shown in FIG. 2B, after aspecific motor is driven at the maximum frequency, the driving speed ofthe specific motor is gradually decreased, and as the driving speed ofthe specific motor is decreased, driving of the other motors starts.Therefore, hand movement time decreases, and movement of the hands isdynamically performed, whereby expressiveness of movement of the handsis improved.

Prior to a detailed description of the timings of FIG. 2B, the operationspecifications of the dual-core motor 12, the first single-core motor15, the second single-core motor 18, and the third single-core motor 21during fast-forwarding will be described with reference to FIG. 3.

FIG. 3 is a view illustrating the maximum drive frequencies and drivepulse lengths of drive pulses which are applied to the motors,respectively. As apparent from FIG. 3, in a case of driving thedual-core motor 12 at 192 pps, since a drive pulse of 3 ms are appliedin each period of 5.2 ms, thereby driving the dual-core motor, it isimpossible to drive the dual-core motor in parallel with any othermotor. As shown in FIG. 3, in order to drive any other motor, it isrequired to apply drive pulses having a drive pulse length of 3.5 ms. Ifparallel driving is performed at 192 pps, in two motors, motor drivecurrents are generated at the same time. As a result, the drive currentincreases, whereby an excessive load is applied on the power source unit26. For this reason, in the electronic watch 100 of the presentembodiment, in a case where the drive pulses which are applied to themotors do not overlap each other, the motors are driven in parallel.

Specifically, in order to drive the dual-core motor 12 and the firstsingle-core motor 15 in parallel, control is performed on a drivecontrol signal for applying drive pulses to the dual-core motor 12 and adrive control signal for applying drive pulses to the first single-coremotor 15, as follows. The drive pulse generating unit 2302 of the microcomputer 23 disables the drive control signal of the dual-core motor 12(for example, switching of the drive control signal to the low level),and then enables the drive control signal of the first single-core motor15 (for example, switching of the drive control signal to the highlevel), or disables the drive control signal of the first single-coremotor 15 and then enables the drive control signal of the dual-coremotor 12.

According to the driving timings of FIG. 2B, first, drive pulses areapplied to the dual-core motor 12 at the maximum drive frequency of 192pps for a predetermined period, whereby the disk hand 10 is moved. Ifthe number of remaining drive steps of the dual-core motor 12 becomes60, the drive pulse rate of the dual-core motor 12 is decreased to 128pps. At this time, the drive pulse period becomes 7.8 ms, and thereforeit is possible to drive the first single-core motor 15 having the drivepulse length of 3.5 ms in parallel with the dual-core motor. Therefore,when the drive pulse rate of the dual-core motor 12 is decreased to 128pps, the first single-core motor 15 is driven at 64 pps, in parallelwith driving of the dual-core motor, thereby starting fast-forwarding.

Thereafter, if the number of remaining drive steps of the dual-coremotor 12 becomes 30, the drive pulse rate of the dual-core motor 12 isdecreased to 64 pps. At this time, the drive pulse period becomes 15.6ms, and therefore it is possible to drive the first single-core motor 15and the second single-core motor 18 having the drive pulse lengths of3.5 ms in parallel with driving of the dual-core motor. Therefore, whenthe drive pulse rate of the dual-core motor 12 is decreased to 64 pps,in addition to the first single-core motor 15, the second single-coremotor 18 is driven at 64 pps, in parallel with driving of the dual-coremotor, thereby starting fast-forwarding.

When driving of the dual-core motor 12 finishes, the first single-coremotor 15 and the second single-core motor 18 are being driven at 64 pps,and the drive pulse period at this moment is 15.6 ms. Since the drivepulse lengths of the first single-core motor 15 and the secondsingle-core motor 18 are 3.5 ms, it is possible to further drive thethird single-core motor 21 in parallel with driving of the first andsecond single-core motors. Therefore, when driving of the dual-coremotor 12 finishes, in parallel with driving of the first single-coremotor 15 and the second single-core motor 18, the third single-coremotor 21 is driven at 64 pps, and fast-forwarding of the thirdsingle-core motor 21 starts.

As described above, after the dual-core motor 12 is driven at themaximum frequency, and then the driving speed is gradually decreased,and as the driving speed of the dual-core motor 12 is decreased, drivingof the first single-core motor 15, the second single-core motor 18, andthe third single-core motor 21 sequentially starts.

FIG. 2C is a view illustrating an example in which the electronic watch100 of the present embodiment performs fast-forwarding of the hands atother motor driving timings. In the example of FIG. 2C, as the drivingspeed of the dual-core motor 12 decreases, parallel driving of the firstsingle-core motor 15, the second single-core motor 18, and the thirdsingle-core motor 21 starts.

The dual-core motor 12 is driven at the maximum drive frequency of 192pps, thereby starting fast-forwarding of the hand. This driving isperformed for a predetermined period, and if the number of remainingdrive steps becomes 60, the drive frequency of the dual-core motor 12 isdecreased to 128 pps. At this time, it is determined whether it ispossible to further drive the first single-core motor 15, the secondsingle-core motor 18, and the third single-core motor 21 in parallelwith driving of the dual-core motor. This determination is performed onthe basis of whether the drive period of the dual-core motor 12 islonger than the sum of the drive pulse lengths of the individual motorsto be driven in parallel. Specifically, since the drive period of thedual-core motor 12 is 7.8 ms, and the sum of the drive pulse lengths ofthe individual motors to be driven in parallel is 13.5 ms, paralleldriving is not possible. Therefore, only the dual-core motor 12 isdriven at 128 pps for a predetermined period.

If the number of remaining drive steps of the dual-core motor 12 is 30,the drive pulse frequency of the dual-core motor 12 is decreased to 64pps. At this time, since the drive period of the dual-core motor 12becomes 15.6 ms is longer than the sum of the drive pulse lengths of theindividual motors to be driven in parallel, parallel driving becomespossible. Therefore, the first single-core motor 15, the secondsingle-core motor 18, and the third single-core motor 21 are driven at afrequency of 32 pps in parallel with the dual-core motor, therebystarting to fast-forward.

When driving of the dual-core motor 12 finishes, the drive pulse ratesof the first single-core motor 15, the second single-core motor 18, andthe third single-core motor 21 are increased to 64 pps. At this time,since the drive period becomes 15.6 ms longer than the sum of the drivepulse lengths of the first single-core motor 15, the second single-coremotor 18, and the third single-core motor 21, parallel driving ispossible.

As a result of this control, it is possible to perform movement of thehands in a fade-out/fade-in manner in which increasing of the movementspeeds of the hour hand 13, the second/minute interlocking hand 16, andthe function hand 19 is interlocked with decreasing in the movementspeed of the disk hand 10.

As described above, in the motor drive control of the electronic watch100 of the present embodiment, when the drive frequency of the dual-coremotor decreases, if the drive period of the dual-core motor 12 is longerthan the sum of the drive pulse length of the dual-core motor 12 and thedrive pulse lengths of the motors to be sequentially or simultaneouslydriven in parallel, parallel driving is performed.

In the above description, as the driving speed of the dual-core motor 12decreases, the other motors are driven in parallel. However, other motorcombinations are possible.

Now, the flow of control at the driving timings of FIG. 2B will bedescribed with reference to FIG. 4.

First, in STEP S401, the dual-core motor 12 starts to be driven at 192pps. After driving is performed for a predetermined period, in STEPS402, the driving speed of the dual-core motor 12 is decreased to 128pps. Further, in STEP S403, it is determined whether it is possible todrive the first single-core motor 15 (referred to as “FIRST MOTOR” inFIG. 4) and the dual-core motor 12 in parallel. As described above, thisdetermination is performed on the basis of whether the drive period ofthe dual-core motor 12 is longer than the sum of the drive pulse lengthof the dual-core motor 12 and the drive pulse length of the firstsingle-core motor 15.

In STEP S403, in a case where that the drive period of the dual-coremotor 12 is not longer than the sum of the drive pulse lengths of themotors, it is determined that parallel driving is impossible (“No” inSTEP S403), and the flow proceeds to STEP S404.

Meanwhile, in STEP S403, in a case where the drive period of thedual-core motor 12 is longer than the sum of the drive pulse lengths ofthe motors, it is determined that parallel driving is possible (“Yes” inSTEP S403), and the flow proceeds to STEP S405.

In STEP S405, the first single-core motor 15 is driven at 64 pps,thereby starting fast-forwarding. Then, after driving is performed for apredetermined period, in STEP S406, the driving speed of the dual-coremotor 12 is decreased to 64 pps.

At this time, in STEP S412, it is determined whether parallel driving ofthe first single-core motor 15, the single-core motor 18 (referred to as“SECOND MOTOR” in FIG. 4), and the dual-core motor 12 is possible. Thisdetermination is performed on the basis of whether the drive period ofthe dual-core motor 12 is longer than the sum of the drive pulse lengthsof the motors to be driven in parallel.

In STEP S412, in a case where that the drive period of the dual-coremotor 12 is not longer than the sum of the drive pulse lengths of themotors, it is determined that parallel driving is impossible (“No” inSTEP S412), and the flow proceeds to STEP S413.

Meanwhile, in STEP S412, in a case where the drive period of thedual-core motor 12 is longer than the sum of the drive pulse lengths ofthe motors, it is determined that it is possible to further drive thefirst single-core motor 15 and the second single-core motor 18 inparallel with driving of the dual-core motor (“Yes” in STEP S412), andthe flow proceeds to STEP S415.

In STEP S415, the second single-core motor 18 is driven at 64 pps,thereby starting fast-forwarding. Then, after driving is performed for apredetermined period, in STEP S416, driving of the dual-core motor 12 isstopped.

Then, in STEP S417, the third single-core motor 21 (referred to as“THIRD MOTOR” in FIG. 4) is driven at 64 pps, thereby performing handfast-forwarding based on parallel driving.

Then, after driving is performed for a predetermined period, in STEPS410, driving of the first single-core motor 15, the second single-coremotor 18, and the third single-core motor 21 is stopped.

In STEP S404, the dual-core motor 12 is driven at 128 pps for apredetermined period, and then the driving speed of the dual-core motor12 is decreased to 64 pps.

Then, in STEP S407, it is determined whether it is possible to drive thefirst single-core motor 15 and the dual-core motor 12 in parallel. Asdescribed above, this determination is performed on the basis of whetherthe drive period of the dual-core motor 12 is longer than the sum of thedrive pulse length of the dual-core motor 12 and the drive pulse lengthof the first single-core motor 15.

In STEP S407, in a case where that the drive period of the dual-coremotor 12 is not longer than the sum of the drive pulse lengths of themotors, it is determined that parallel driving is impossible (“No” inSTEP S407), and the flow proceeds to STEP S408.

Meanwhile, in STEP S407, in a case where the drive period of thedual-core motor 12 is longer than the sum of the drive pulse lengths ofthe motors, it is determined that parallel driving of the dual-coremotor and the first single-core motor 15 is possible (“Yes” in STEPS407), and the flow proceeds to STEP S411.

In STEP S408, the dual-core motor 12 is driven at 64 pps for apredetermined period, and then driving of the dual-core motor 12 isstopped. Then, in STEP S409, parallel driving of the first single-coremotor 15, the second single-core motor 18, and the third single-coremotor 21 is started. Then, after a predetermined period, in STEP S410,driving is stopped.

In STEP S411, parallel driving of the first single-core motor 15 and thedual-core motor is started. Then, the flow proceeds to STEP S413.

In STEP S413, driving is performed for a predetermined period, and thendriving of the dual-core motor 12 is stopped while driving of the firstsingle-core motor 15 is kept.

Then, in STEP S414, driving of the second single-core motor 18 and thethird single-core motor 21 is started, thereby performing handfast-forwarding based on parallel driving.

Then, after driving is performed for a predetermined period, in STEPS410, driving of the first single-core motor 15, the second single-coremotor 18, and the third single-core motor 21 is stopped.

Then, the flow of control at the driving timings of FIG. 2B finishes.

Now, a more specific example of hand movement control of anotherelectronic watch 110 of the embodiment will be described.

FIG. 5 is a view illustrating the dial of the electronic watch 110. Theelectronic watch 110 has various hands such as a main-watch second hand61, a main-watch hour/minute interlocking hand 64, a sub-watch hour hand67 which is a 24-hour hand, a sub-watch minute hand 70, a function hand73, and a disk hand 10, and has a stem 76 and a plurality of buttons 77.

FIG. 6 is a block diagram illustrating the configuration of a drivedevice 111 of the electronic watch 110 shown in FIG. 5.

The disk hand 10 is driven through a gear train mechanism 11 by adual-core motor 12. The main-watch second hand 61 is driven through agear train mechanism 62 by a first single-core motor 63. The main-watchhour/minute interlocking hand 64 is driven through a gear trainmechanism 65 by a second single-core motor 66. The sub-watch hour hand67 is driven through a gear train mechanism 68 by a third single-coremotor 69. The sub-watch minute hand 70 is driven through a gear trainmechanism 71 by a fourth single-core motor 72. The function hand 73 isdriven through a gear train mechanism 74 by a fifth single-core motor75.

The dual-core motor 12, the first single-core motor 63, the secondsingle-core motor 66, the third single-core motor 69, the fourthsingle-core motor 72, and the fifth single-core motor 75 are steppingmotors. A drive circuit 22 separately applies drive pulses to themotors, thereby rotating the motors.

The drive circuit 22 is controlled by a micro computer 23, and has moredrive channels than the drive circuit 22 of FIG. 1 has. The microcomputer 23 also has the same configuration as that of FIG. 1 exceptthat it has a motor drive pattern table 78 to be described below indetail.

Now, hand movement control during a reset operation of a stopwatchfunction of the electronic watch 110 will be described.

In the stopwatch function of the electronic watch 110, minute of elapsedtime is indicated by the sub-watch hour hand 67, and second of elapsedtime is indicated by the sub-watch minute hand 70. Further, elapsed timeis clocked in units of 1/20 seconds by the main-watch hour/minuteinterlocking hand 64. When stopwatch function starts to operate, or whena reset button 77 is pushed for clocking, the main-watch hour/minuteinterlocking hand 64, the sub-watch hour hand 67, and the sub-watchminute hand 70 are fast-forwarded to the zero position of clocking.

In order to implement high expressiveness of hand movement, theelectronic watch 110 of the present embodiment performs hand movementcontrol under the following conditions.

-   -   A condition that three hands of the main-watch hour/minute        interlocking hand 64, the sub-watch hour hand 67, and the        sub-watch minute hand 70 should be able to be moved in parallel        so as to reach the zero position almost at the same time.    -   A condition that hand movement time should be short.    -   A condition that the main-watch hour/minute interlocking hand        64, the sub-watch hour hand 67, and the sub-watch minute hand 70        should be able to rotate in a normal direction and a reverse        direction.    -   A condition that the maximum drive frequencies of the main-watch        hour/minute interlocking hand 64, the sub-watch hour hand 67,        and the sub-watch minute hand 70 should be 64 pps, and the drive        pulse lengths thereof should be 6.0 ms.

As will be described in more detail with reference to FIGS. 7 to 9, theelectronic watch 110 obtains the order of the hands in terms of thenumber of remaining steps for hand movement to the zero position, andstart to fast-forward a hand having the greatest number of remainingsteps, first. Thereafter, in order to start to drive the other hands,the electronic watch determines whether parallel driving is possible. Ina case where parallel driving is not possible, the electronic devicedecreases the drive frequency of the driven hand, and performs paralleldriving of the hands, thereby fast-forwarding three hands such that thehands reach the zero position almost at the same time.

FIG. 7 is a timing chart for explaining the reset operation of thestopwatch function. FIG. 7 shows a case where the number of remainingsteps for hand movement to the zero position increases in the order themain-watch hour/minute interlocking hand 64 (the first single-coremotor), the sub-watch hour hand 67 (the third single-core motor), andthe sub-watch minute hand 70 (the fourth single-core motor).

First, at a timing pt0, the first single-core motor is driven at 64 pps,whereby starting fast-forwarding.

At a timing pt1 which is the driving start timing of the thirdsingle-core motor, it is determined whether parallel driving of thefirst single-core motor and the third single-core motor is possible.This determination is performed on the basis of whether the drive periodof the first single-core motor is longer than the sum of the drive pulselength of the first single-core motor and the drive pulse length of thethird single-core motor. In this case, since the drive period is 15.6ms, and the sum of the drive pulse lengths is 12.0 ms, it is determinedthat parallel driving of the first single-core motor and the thirdsingle-core motor is possible. Therefore, at the timing pt1, the thirdsingle-core motor is driven at 64 pps, whereby starting fast-forwarding.

At a timing pt2 which is the driving start timing of the fourthsingle-core motor, it is determined whether parallel driving of thefirst single-core motor, the third single-core motor, and the fourthsingle-core motor is possible. In this case, since parallel driving ofthree hands at 64 pps is not possible, the drive frequencies of themotors are decreased to 32 pps, and it is determined again whetherparallel driving is possible. In this case, since the drive period 31.2ms, and the sum of the drive pulse lengths is 18.0 ms, it is determinedthat parallel driving of the first single-core motor, the thirdsingle-core motor, and the fourth single-core motor is possible.Therefore, at the timing pt2, the first single-core motor and the thirdsingle-core motor are decelerated to 32 pps, and the fourth single-coremotor is driven at 33 pps, thereby starting fast-forwarding.

In this hand driving timing control, since the numbers of remainingsteps for hand movement to the zero position are obtained in advance,and then fast-forwarding of each of the hands is started, if driving ofthe first single-core motor, the third single-core motor, and the fourthsingle-core motor is stopped at a timing pt3, the main-watch hour/minuteinterlocking hand 64, the sub-watch hour hand 67, and the sub-watchminute hand 70 reach the zero position almost at the same time.

FIG. 8 is a view illustrating the operation conditions of the motorsduring the reset operation, and shows the drive frequencies in the handmovement ranges of the first single-core motor, the third single-coremotor, and the fourth single-core motor described with reference to FIG.7.

In the hand reset operation, the fast-forward start positions and thezero position are determined before the hands are moved. Therefore, itis possible to obtain the operation conditions of FIG. 8 before drivingof the motors, and it is also possible to fast-forward the hands to thezero position by driving the motors according to those operationconditions.

FIG. 9 is a view illustrating the flow of control for obtaining theoperation conditions shown in FIG. 8 and performing motor drive control.

First, in STEP S901, with respect to each of the hands, the number ofremaining steps for hand movement to the zero position is obtained.

Subsequently, in STEP S902, processing to STEP S908 is repeated on thehands in descending order from the hand having the greatest number ofremaining steps, whereby the operation conditions of the motors areobtained.

In STEP S903, the drive start step position of the corresponding hand isobtained.

Subsequently, in STEP S904, it is determined whether the currentposition is a step position to drive a plurality of hands (a number ofhands). If the current position is not a step position to drive aplurality of hands (“No” in STEP S904), in STEP S910, the drivefrequency of the hand is set to the maximum frequency. Then, the flowproceeds to STEP S907. Meanwhile, if the current position is a stepposition to drive a plurality of hands (“Yes” in STEP S904), in STEPS905, it is determined whether parallel driving is possible.

If it is determined in STEP S905 that parallel driving is possible(“Yes” in STEP S905, in STEP S910, the drive frequency of the hand isset to the maximum frequency. Then, the flow proceeds to STEP S907.Meanwhile, if it is determined that parallel driving is not possible(“No” in STEP S905), the drive frequency of the hand is set to a lowerfrequency at which parallel driving is possible. Then, the flow proceedsto STEP S907.

In STEP S907, the hand movement range and the drive frequency are set ina drive table (the motor drive pattern table 78 of FIG. 6).

Subsequently, in STEP S908, processing of STEPS S903 to S907 is repeatedon the other hands.

Next, in STEP S909, the motors are driven according to the drive table,whereby the hands are moved.

In this flow, it is possible to perform the hand movement of the resetoperation of the stopwatch function of the electronic watch 110described with reference to FIG. 7.

The hand movement control during the reset operation of the stopwatchfunction of the electronic watch 110 described with reference to FIGS. 7to 9 can also be applied to a flyback operation of the stopwatchfunction.

FIG. 10 is a timing chart for explaining the operation of the flybackfunction of a stopwatch, and FIG. 11 is a view illustrating the flow ofcontrol of the flyback function of the stopwatch.

As shown in FIG. 10, if a button 77 of the electronic watch 110 ispushed (“Push”), driving of the first single-core motor, the thirdsingle-core motor, and the fourth single-core motor stops, wherebyclocking of the stopwatch stops. Thereafter, movement of the main-watchhour/minute interlocking hand 64, the sub-watch hour hand 67, and thesub-watch minute hand 70 to the zero position described with referenceto FIG. 7 is performed (the reset operation). After resetting of thehands finishes, if the button 77 is released (“off”), clocking of thestopwatch restarts.

Now, the control flow of the flyback function of FIG. 11 will bedescribed.

First, in STEP S1101, it is waited for the button 77 of the electronicwatch 110 to be pushed.

If it is determined in STEP S1101 that the button 77 is pushed (“Yes” inSTEP S1101), in STEP S1102, clocking of the stopwatch is stopped.

Subsequently, in STEP S1103, processing of the hand reset operationdescribed with reference to FIG. 9 is performed.

If the hand reset operation finishes, in STEP S1104, it is waited forthe button 77 to be released.

If the button 77 is released (“No” in STEP S1104), in STEP S1105,clocking of the stopwatch is restarted.

By the above described processing, it is possible to perform the flybackoperation of the stopwatch function.

Although the embodiment has been described with reference to theelectronic watches having analog hands, the embodiment is not limitedthereto, and can also be applied to any other clocking device whichperforms display by analog hands.

What is claimed is:
 1. A drive device comprising: a first hand; a second hand; and a control unit that controls a movement operation of the second hand, wherein: the control unit starts movement of the second hand in a period after start of movement of the first hand and before stop of the movement of the first hand, and the control unit controls the movement operation of the second hand according to a decrease in a movement speed of the first hand.
 2. The drive device according to claim 1, wherein: after starting the movement of the second hand, the control unit changes a movement speed of the second hand according to the decrease in the movement speed of the first hand.
 3. The drive device according to claim 1, wherein: after controlling the movement operation of the second hand according to the decrease in the movement speed of the first hand, the control unit stops the movement of the second hand according to a stop timing of the first hand.
 4. The drive device according to claim 2, wherein: after controlling the movement operation of the second hand according to the decrease in the movement speed of the first hand, the control unit stops the movement of the second hand according to a stop timing of the first hand.
 5. The drive device according to claim 1, further comprising: a third hand, wherein: the control unit further controls a movement operation of the third hand, after starting the movement of the second hand, the control unit starts movement of the third hand, and when the movement speed of the first hand further decreases after starting the movement of the second hand according to the decrease in the movement speed of the first hand, the control unit controls the movement operation of the third hand.
 6. The drive device according to claim 2, further comprising: a third hand, wherein: the control unit further controls a movement operation of the third hand, after starting the movement of the second hand, the control unit starts movement of the third hand, and when the movement speed of the first hand further decreases after starting the movement of the second hand according to the decrease in the movement speed of the first hand, the control unit controls the movement operation of the third hand.
 7. The drive device according to claim 3, further comprising: a third hand, wherein: the control unit further controls a movement operation of the third hand, after starting the movement of the second hand, the control unit starts movement of the third hand, and when the movement speed of the first hand further decreases after starting the movement of the second hand according to the decrease in the movement speed of the first hand, the control unit controls the movement operation of the third hand.
 8. The drive device according to claim 4, further comprising: a third hand, wherein: the control unit further controls a movement operation of the third hand, after starting the movement of the second hand, the control unit starts movement of the third hand, and when the movement speed of the first hand further decreases after starting the movement of the second hand according to the decrease in the movement speed of the first hand, the control unit controls the movement operation of the third hand.
 9. The drive device according to claim 5, wherein: the movement speed of the first hand at which the control unit starts the movement of the second hand is twice the movement speed of the first hand at which the control unit starts the movement of the third hand.
 10. The drive device according to claim 1, further comprising: an operation unit configured to receive a user's operation, wherein: the control unit further control a movement operation of the first hand, and when the operation unit receives the user's operation, the control unit starts the movement of the first hand.
 11. The drive device according to claim 2, further comprising: an operation unit configured to receive a user's operation, wherein: the control unit further control a movement operation of the first hand, and when the operation unit receives the user's operation, the control unit starts the movement of the first hand.
 12. The drive device according to claim 3, further comprising: an operation unit configured to receive a user's operation, wherein: the control unit further control a movement operation of the first hand, and when the operation unit receives the user's operation, the control unit starts the movement of the first hand.
 13. The drive device according to claim 4, further comprising: an operation unit configured to receive a user's operation, wherein: the control unit further control a movement operation of the first hand, and when the operation unit receives the user's operation, the control unit starts the movement of the first hand.
 14. An electronic watch comprising the drive device according to claim
 1. 